1. Field of the Invention
The invention relates to methods for performing a variety of operations on a die or dental model using cyanoacrylate compounds. In particular, the methods include the use of cyanoacrylate compounds to base up and block out voids, deep areas, undercuts, and the like on a die model as well as to index dental crowns on a die model for investment soldering and to aid in fabricating porcelain jacket crowns and unbreakable die models.
2. Description of the Prior Art
Die models are commonly used in dental laboratories for a number of well-known dental fitting and fabrication purposes. Typically, a model is formed of a gypsum or epoxy material by casting from a negative impression mold of the teeth made in a dentist's office. The die model is then used to fabricate, size, and pre-fit dental appliances such as crowns, porcelain jacket crowns, indexed multiple crowns and the like. In order for these appliances to fit properly in the mouth, the model must accurately represent the structural condition of the teeth and must be free of flaws which often result due to the nature of the tooth preparation, impression process and of the casting process. Further, dental models must often be modified to reflect the structural condition of the teeth which should exist at the time of fitting of an appliance even though such a condition did not exist at the time the impression mold was made. Exemplary of such flaws and conditions which must be corrected on the model are bubble voids which occur in the casting process, undercuts which occur usually in the tooth preparation process, and deep areas which often result on removal of decay and which are not filled in on the tooth prior to impression molding. These voids, undercuts, and deep areas must be filled in, blocked out, or based up as necessary in order to produce a model of the tooth which is proper for seating or fitting a crown or other appliance on the model of the tooth without resistance. Once the model itself has been properly prepared, operations such as the indexing of two or more dental crowns and subsequent transfer to a solder investment are often required. In some situations, the model itself must be unbreakable in order to index a bridge or precision partial abutment.
Dental technicians have developed considerable skills in preparing die models for use and for working with the die models once prepared. However, the materials and techniques heretofore available to the technician have inherently resulted in lost time due not only to material failures but also to the lengthy time periods required for adequate solidification or curing of a material before subsequent operations can be performed on the model. In order to perform these operations both efficiently and effectively, the technician requires a material which can conveniently be used with a minimum of cleaning of the work area, which requires a minimum of time for setting or curing, which has acceptably low shrinkage, and which is not susceptible to melt-through when contacted with molten wax. Prior materials used by the dental technician have failed to meet with all of the above requirements even though substantial investments of time and resources have been directed toward the indentification and development of a material capable of exhibiting the stated characteristics. Traditionally, various waxes and similar compounds have been used and are now in widespread use in spite of the many shortcomings of these materials. In use, a wax has been melted and flowed into an undercut or the like, the wax then being smoothed out with a heated instrument. Specialized equipment, such as a heat source and the like, is thus required. The necessity for such equipment adds expense to the operation of a dental laboratory and thus requires additional maintenance for the equipment and effort in maintaining the work area in an orderly condition. When subsequent operations require the application of additional molten wax to the model which has been prepared with a wax material, the subsequently applied wax often adheres to the wax used to prepare the model, even though a lubricant is conventionally applied to the prepared model. When the subsequently applied wax adheres to or flows through or into the wax used to prepare the model, the wax tooth model sculpted from the subsequently applied wax invariably breaks when removed from the model, thereby resulting in a significant loss of time and labor. Such problems are also a cause of undeniable and previously unavoidable frustration to the technician. This most commonly used of die preparation materials also presents clean-up problems which occur during the finishing and polishing of cast crowns and the like. In such situations, should the technician fail to remove any adhering wax, processing heat melts the wax or similar dental compound to the inside of the crown, thereby requiring additional labor cost to clean both the die model and the crown.
The use of a base-up material such as a gypsum product, the material from which most die models are cast, requires water soaking of the die model to facilitate adhesion of the base-up material, the time delays thus inherent in such a process being usually unacceptable to an orderly progression of work within a dental laboratory. Further, such a material does not adhere well to an unsoaked model and does not set sufficiently rapidly to prevent undesirable flow of the material into other areas of the model, thus requiring removal of the unwanted material or scrapping of the ruined model. Certain other materials used for preparation of dental models require the use of expensive equipment such as ultraviolet radiation generators which are necessary for curing, these ultraviolet cured materials being much more expensive than other candidate materials. Due to the potential for hazard in the use of ultraviolet radiation, many dental technicians hesitate to use a material if so cured. Polymeric materials previously used as base-up materials have required mixing of liquids and powders, the mixtures requiring substantial time to sufficiently thicken to allow application to the model. Once applied, these materials do not rapidly cure to a hard set and, when set, exhibit unacceptable shrinkage of up to 15%. Use of these polymeric materials requires a substantial and unavoidable cleaning of the work area.
The present invention contemplates the use of materials which exhibit all of the characteristics referred to above as being important to the preparation of a dental model and to the performance of various operations on a prepared model. In particular, the invention provides an inexpensive material which requires no extraordinary use precautions, which requires no mixing or after-use clean-up, which sets in a minimum of time to a hardened condition not susceptible to wax flow-through or adherence, and which does not exhibit an unacceptable degree of shrinkage. The methods according to the present invention involve the use of high viscosity cyanoacrylate compounds which are hardened through the use of an accelerator, particularly by the application of an atomized mist of an accelerator, whether or not in a volatile solvent, to the cyanoacrylate compound previously positioned on the model. Substantial savings of time and labor result through practice of the present methods, certain heretofore unobtainable advantages to be hereinafter described being realized according to the teaching of the present invention.